Inspection apparatus for circuit pattern

ABSTRACT

In a circuit pattern inspection apparatus, while an electron beam is irradiated onto a surface of a substrate having a plurality of chips where circuit patterns have been formed, a signal produced from the irradiated substrate is detected so as to form an image, and then, the formed image is compared with another image in order to detect a defect on the circuit patterns. Before the electron beam is irradiated onto either the chip or the plurality of chips so as to acquire the image for an inspection purpose, an electron beam is previously irradiated onto the region to be irradiated, so that charging conditions of the substrate to be inspected are arbitrarily controlled.

BACKGROUND OF THE INVENTION

The present invention is related to an inspection apparatus forinspecting circuit patterns of semiconductor devices formed onsemiconductor wafers, circuit patterns of photomasks formed thereon, andthe like.

As methods for inspecting defects which are present in circuit patternsformed on substrates, or boards to be inspected, e.g., semiconductorwafers and photomasks, inspection apparatus using electron beams andcapable of accepting very fine processing of circuit patterns are knownin this field in addition to inspection apparatus using optical images.

This inspection apparatus is designed in such a manner that SEM(Scanning Electron Microscope) is applied thereto, by which an image isproduced from secondary electrons and reflected electrons, which aregenerated by irradiating an electron beam onto a substrate to beinspected. This inspection apparatus compares SEM images as to the samecircuit pattern with each other so as to extract different pixels fromthe SEM image, and thus, recognizes these different pixels as defects.

In this inspection apparatus, image qualities of acquired SEM images aredifferent from each other, depending upon a total number of irradiatingoperations of the electron beams with respect to the substrate to beinspected. When a total number of the electron beam irradiatingoperations is small, since an information amount as to an acquiredinspection region is small, such a technique is known from, for example,JP-A-5-258703. That is, the same inspection region is irradiated pluraltimes in order to acquire a sufficiently large number of images for aninspection purpose.

Otherwise, when a total number of the electron beam irradiatingoperations is large, since irradiation energy is high, there is such aproblem that image contrast is changed due to a charging effect of thesubstrate to be inspected. As a result, another technique capable ofacquiring an image by irradiating an electron beam one time is knownfrom, for example, JP-A-2000-193594.

In this inspection apparatus, in such a case that an image is acquiredby irradiating the electron beam one time, the following problems mayoccur due to a property of a substrate to be inspected. That is,contrast of the acquired image is fluctuated, and also, sufficientlyhigher contrast as to a subject portion cannot be obtained, since theelectron beam is irradiated one time. To solve the above-explainedproblems, one solving method is performed in such a manner that sincethe same region of the image is irradiated by the electron beams pluraltimes, an irradiation energy amount of the electron beams is increased.In this case, it is so assumed that a single transport of the substrateto be inspected which is transported along one direction while beingscanned by an electron beam is referred to as a “line.” Thus, in thecase of a single irradiating operation, after a scanning operation of 1line is accomplished, the substrate to be inspected is transported by 1line along a direction perpendicular to the line, and then, an adjoiningline is irradiated by an electron beam, whereas in the case of a pluralirradiating operation, 1 line is irradiated plural times withouttransporting the substrate to be inspected along the perpendiculardirection.

However, if the irradiation energy amount is increased in such a method,then there is such a risk. That is, a potential is locally andtemporarily changed, so that a semiconductor wafer corresponding to thesubstrate to be inspected is destroyed. Also, since the same line isirradiated plural times, inspection time is delayed.

SUMMARY OF THE INVENTION

An object of the present invention is to provide such an inspectionapparatus for inspecting a circuit pattern, while the circuit patterninspection apparatus is capable of arbitrarily controlling a chargingcondition of a substrate to be inspected, and employs an electron beamhaving high reliability.

To achieve the above-described object, a circuit pattern inspectionapparatus, according to an embodiment of the present invention, isfeatured by comprising a condition setting means for setting aninspection condition in such a manner that before an electron beam isirradiated onto either a chip or a plurality of chips so as to acquirean image for an inspection purpose, an electron beam is previouslyirradiated onto the region to be irradiated. Since this arrangement isemployed, this circuit pattern inspection apparatus is equipped withsuch a function. That is, in the case that an inspecting operation of awafer is carried out, before an image of this wafer for an inspectionpurpose is acquired, since an electron beam is irradiated onto the sameportion, a charging condition of the wafer is changed, and thus, bothbrightness and contrast of an inspection image are changed.

Also, a circuit pattern inspection apparatus, according to anotherembodiment of the present invention, is featured by that a conditionsetting means for setting an inspection condition in such a manner thatafter an electron beam is irradiated onto either a chip or a pluralityof chips so as to acquire an image for an inspection purpose, anelectron beam is again irradiated onto the region to be irradiated.Since this arrangement is employed, this circuit pattern inspectionapparatus is equipped with such a function. That is, a chargingcondition of a wafer is changed in order that electric charges are notstored, or the charging operation is accelerated.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view for showing a schematicarrangement of an inspection apparatus for inspecting a circuit pattern,according to an embodiment of the present invention.

FIG. 2 is a screen diagram for representing a display example of animage operation unit of the circuit pattern inspection apparatus shownin FIG. 1.

FIG. 3 is a flow chart for describing sequential process operations of arecipe forming mode executed in the circuit pattern inspectionapparatus.

FIG. 4 is a screen diagram for indicating a display example when therecipe is formed.

FIG. 5 is a plan view for indicating an array of chips on a substrate tobe inspected.

FIG. 6 is a screen diagram for setting parameters when the recipe isformed.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to drawings, an inspection apparatus for inspecting acircuit pattern, according to an embodiment of the present invention,will be described in detail. In this embodiment, defects occurred inmanufacturing steps of circuit patterns formed on semiconductor wafersare extracted. The inspection apparatus is used to extract defects as toa resist pattern, a CONT-system opening pattern, a fine pattern afteretching process (diffusion system), a fine pattern after etching process(wiring system), and the like.

FIG. 1 is a longitudinal sectional view for showing a schematicarrangement of an inspection apparatus 1 for inspecting a circuitpattern, according to an embodiment of the present invention. To thecircuit pattern inspection apparatus 1, a secondary electron detectingunit 7, a control computer 6, and an image operation unit 5 areconnected. The secondary electron detecting unit 7 converts a secondaryelectron detecting signal (will be discussed later) into an electricsignal. The control computer 6 stores an electric image signal detectedfrom the secondary electron detecting unit 7 so as to reduce noise andincrease/decrease a signal, and also, transfers an instruction signal toa correction control circuit 43. The image operation unit 5 is equippedwith a monitor which displays thereon either a result of defectextracting operation or an image thereof on a screen, and equipped withan input tool for an instruction of an operator.

The circuit pattern inspection apparatus 1 is provided with aninspection chamber 2 and an auxiliary chamber (not shown in thisembodiment). In the inspection chamber 2, an interior portion of thischamber 2 is vacuum-exhausted. The auxiliary chamber is used totransport a substrate 9 to be inspected such as a semiconductor wafer tothe inspection chamber 2. It should be noted that this auxiliary chamberis constructed in such a manner that the auxiliary chamber can bevacuum-exhausted in an independent manner from the inspection chamber 2.

The inspection chamber 2 is mainly constituted by an electro-opticalsystem 3, a sample chamber 8, and an optical microscope unit 4. Theelectro-optical system 3 is arranged by an electron gun 10, anextracting electrode 11, a condenser lens 12, a blanking deflectingdevice 13, a scanning deflecting device 15, a diaphragm 14, an objectivelens 16, a reflection plate 17, and an ExB deflecting device 18. In thiselectro-optical system 3, an electron beam 19 generated by the electrongun 10 is converged by the condenser lens 12 and the objective lens 16,and then, the converged electron beam 19 is irradiated onto thesubstrate 9 to be inspected.

An orbit of secondary electrons 37 which are produced from the substrate9 to be inspected by irradiating the electron beam 19 onto thissubstrate 9 is deflected by the ExB deflecting device 18, and thesecondary electrons 37 impinge on the reflection plate 17, so thatsecond secondary electrons 38 are generated therefrom. The secondsecondary electrons 38 are detected by a secondary electron detector 20,the detection signal of this secondary electron detector 20 is suppliedto the secondary electron detecting unit 7, and the signal derived fromthe secondary electron detecting unit 7 is amplified by a preamplifier21 of this secondary electron detecting unit 7. Then, the signalamplified by the preamplifier 21 is A/D-converted into digital data byan A/D converter 22, the digital data is fed to an optical convertingmeans 23 so as to be converted into an optical signal, and this opticalsignal is transferred by an optical transferring means 24. Then, thisoptical signal is again converted into an electric signal, andthereafter, this electric signal is supplied to the control computer 6.

The secondary electron detecting unit 7 is provided with a preamplifier21, an A/D converter 22, an optical converting means 23, an opticaltransferring means 24, an electric converting means 25, a high voltagepower supply 26, a preamplifier driving power supply 27, anA/D-converter driving power supply 28, and a reverse biasing powersupply 29. Since this secondary electron detecting unit 7 is broughtinto a floating condition at a positive potential by the high voltagepower supply 26, the second secondary electrons 38 which have impingedonto the reflection plate 17 to be generated are conducted to thesecondary electron detector 20 by an absorbing electric field which isproduced.

The sample chamber 8 is constructed of a sample stage 30, an X stage 31,a Y stage 32, a rotary stage 33, a position monitor length measuringmachine 34, and a measuring machine 35 for measuring a height of asubstrate to be inspected.

The optical microscope unit 4 has a light source 40, an optical lens 41,and a CCD (charge-coupled device) camera 42. This optical microscopeunit 4 is located in the vicinity of the electro-optical system 3employed inside the inspection chamber 2 and is installed at such aposition that this optical microscope unit 4 is separated from theelectro-optical system 3 while there is no mutual influence betweenthem. The distance between the electro-optical system 3 and the opticalmicroscope unit 4 is known in this field.

Either the X stage 31 or the Y stage 32 may be moved in a reciprocationmanner over the predetermined distance between the electronic opticalsystem 3 and the optical microscope unit 4. Also, either the rotarystage 33 or the sample stage 30 may be alternatively arranged in such amanner that an arbitrary side of this stage 33 or 30 is inclined so thatan angle at which the electron beam 19 is irradiated onto the substrate9 to be inspected may be varied.

The control computer 6 is arranged by an entire control unit 65 and thebelow-mentioned apparatus. That is, this control computer 6 contains astorage means 61, an image processing circuit 62, a process parametersetting unit 48, and also, a defect data buffer 63. The storage means 61stores thereinto a digital signal derived from the secondary electrondetecting unit 20. The image processing unit 62 processes the storeddigital signal. The process parameter setting unit 48 sets a processparameter of the image processing circuit 62. The defect data buffer 63buffers thereinto information as to a defect extracted by the defectjudging unit 54 of the image operation unit 5.

On a screen 50 of the image operation unit 5, positions as to aplurality of defects held in the defect data buffer 63 can be displayedin a wafer map by way of dots, and/or an image of a defect stored in thestorage means 61 can be displayed.

The image operation unit 5 contains a first image storage unit 51, asecond image storage unit 52, a comparing/calculating unit 53, and adefect judging unit 54. Such an image as an electron beam image and adefect image is displayed on an image display portion 56 of the screen50 such as a monitor. Also, the screen 50 is provided with a map displayportion 55, an image acquisition instructing portion 57, an imageprocess instructing portion 58, and a process condition setting portion59. The map display portion 55 displays thereon a plan view of thesubstrate 9 to be inspected so as to set an inspection region, anddisplays thereon a distribution of extracted defects. Furthermore, thisscreen 50 contains a mode switching portion 60 for designating aninspection mode, a defect confirmation mode, a recipe formation mode, autility mode, and the like in accordance with an content of anoperation.

The map display portion 55 is clicked by using a mouse (not shown), orthe like so as to move the X stage 31 and the Y stage 32, and thus aplace for setting a condition is selected. Also, since the imageacquisition instructing unit 57 is clicked, the electron beam 19 isirradiated onto the substrate 9 to be inspected, so that an image of aninspection region is acquired. The process condition setting portion 59can set such a process condition that a signal of an image is increasedand/or decreased. When the image process instructing portion 58 isclicked, this set process condition is executed.

Operation commands and operation conditions as to various units of thecircuit pattern inspection apparatus 1 are inputted/outputted from theimage operation unit 5. Various conditions have been previously enteredto the image operation unit 5 in such a manner that these conditions maybe set in response to a purpose, while these various conditionscorrespond to an acceleration voltage when the electron beam 19 isgenerated, a deflection width of the electron beam 19, a deflectionspeed of the electron beam 19, signal acquisition timing of thesecondary electron detecting unit 7, a move speed of the sample stage30, and the like.

In response to the above-described signal supplied from the imageoperation unit 5, the control computer 6 sends a control signal to acorrection control circuit 43. The correction control circuit 43monitors a shift of a position and a shift of a height based upon asignal derived from the position monitor length measuring device 34 andanother signal derived from the inspecting-substrate-height lengthmeasuring device 35. As a result of this monitoring operation, thecorrection control circuit 43 produces a correction signal, and thentransfers the correction signal to the objective lens power supply 45and a scanning signal generator 44 in such a manner that the electronbeam 19 may be continuously irradiated onto a correct position.

In order to acquire an image of the substrate 9 to be inspected, such anelectron beam 19 which has been focused in a narrow mode is irradiatedonto the substrate 9 to be inspected so as to generate secondary beams37, and these secondary beams 37 are detected in synchronism with boththe scanning operation of the electron beam 19, and the movement of theX stage 31 and of the Y stage 32, so that an image of a surface of thesubstrate 9 to be inspected is acquired.

When a semiconductor wafer is inspected, it is desirable that aninspection speed becomes high. As a consequence, in the circuit patterninspection apparatus 1 of this embodiment, such an operation is notcarried out. That is, as executed in the normal SEM, an electron beam ofan electron beam current on the order of “pA” is scanned in a low speed,a scanning operation is carried out many times, and the respectiveimages are overlapped with each other. Also, in order to suppresscharging operation to an insulating material, an electron beam must bescanned in a high speed one time, or several times.

In this embodiment, the circuit pattern inspection apparatus 1 has beenconstituted in such a manner that since a large current electron beamof, for instance, 100 nA is scanned only one time, which isapproximately 100 times larger than that of the normal SEM, an image isformed. A scanning width is selected to be 100 m², one pixel is selectedto be 0.1 μm², and a single scanning operation is carried out within atime period of 1 μs.

As the electron gun 10, a diffusion supply type thermal field emissionelectron source is used. Since this electron gun 10 is employed, astable electron beam current can be secured, and thus, an SEM imagehaving a small bright variation can be obtained, as compared with theconventional tungsten electron source, and a cold electric fieldemission mode electron source. Also, since the electron beam current canbe set to a large electron beam current by this electron gun 10, ahigh-speed inspection can be realized.

Since a voltage is applied between the electron gun 10 and theextracting electrode 11, the electron beam 19 is extracted from theelectron gun 10. Also, since a negative high potential is applied to theelectron gun 10, the electron beam 19 is accelerated. The electron beams19 are propagated along a direction of the sample stage 30 with havingsuch an energy equivalent to this applied potential, the propagatedelectron beams 19 are converged by the condenser lens 12, and further,the converged electron beams 19 are focused to be narrowed by theobjective lens 16, and then, the focused electron beam 19 is irradiatedonto the substrate 9 to be inspected which is mounted on the X stage 31and the Y stage 32 on the sample stage 30. It should be noted that thesubstrate 9 to be inspected corresponds to a semiconductor wafer, asemiconductor chip, or liquid crystal, and a substrate having a veryfine circuit pattern such as a mask.

It should also be noted that the scanning signal generator 44 isconnected to the blanking deflecting device 13, by which both a scanningsignal and a blanking signal are generated, whereas the objective lenspower supply 45 is connected to the objective lens 16.

A negative voltage is applied to the substrate 9 to be inspected by aretarding power supply 36. Since the negative voltage of this retardingpower supply 36 is adjusted, the electron beam 19 can be decelerated,and electron beam irradiation energy with respect to the substrate 9 tobe inspected can be controlled to be an optimum energy value while thepotential of the electron gun 10 is not changed. The secondary electron37 generated by irradiating the electron beam 19 onto the substrate 9 tobe inspected is accelerated by the negative voltage applied to thesubstrate 9 to be inspected.

The ExB deflecting device 18 is arranged above the substrate 9 to beinspected, so that the secondary electron 37 is deflected along apredetermined direction. An amount of this deflecting operation can beadjusted based upon both a voltage and a strength of a magnetic field,which are applied to the ExB deflecting device 18. Also, thiselectromagnetic field can be varied in an interlocking manner with thenegative voltage applied to the substrate 9 to be inspected. Thesecondary electron 37 deflected by the ExB deflecting device 18 impingeson the reflection plate 17. This reflection plate 17 has a circular coneshape, and is manufactured with a pipe structure in an integral form inorder to have a shielding function of a deflecting device for theelectron beam which is irradiated onto the substrate 9 to be inspected.When the accelerated secondary electron 37 impinges on this reflectionplate 17, the second secondary electrons 38 having energy of several eVto 50 eV are produced from the reflection plate 17.

The secondary electron detector 20 is constructed as follows: The secondsecondary electron 38 generated in such a manner that the secondaryelectron 37 generated while the electron beam 19 has been irradiatedonto the substrate 9 to be inspected is thereafter accelerated and thenthis accelerated secondary electron 37 impinges on the reflection plate17 is detected in an interlocking manner with respect to the scanningtiming of the electron beam 19.

An output signal of the secondary electron detector 20 is amplified bythe preamplifier 21 of the secondary electron detecting unit 7 which isinstalled outside the inspection chamber 2, and then, the amplifiedsignal is A/D-converted by the A/D converter 22 to become digital data.The A/D converter 22 is constituted in such a manner that just after theanalog signal detected by the secondary electron detector 20 isamplified by the preamplifier 21, the A/D converter 22 converts theamplified analog signal into the digital signal, and then, this digitalsignal is transmitted to the control computer 6. Since the detectedanalog signal is digitized just after the detection and then thisdigitized signal is transmitted, such a signal having a high S/N ratiocan be acquired in a high speed.

While the substrate 9 to be inspected is mounted on the X stage 31 andthe Y stage 32, when an inspecting operation is carried out, both the Xstage 31 and the Y stage 32 are set to a stationary condition, and theelectron beam 19 is scanned in a two-dimensional manner. Otherwise,while the Y stage 32 is continuously moved at a constant speed along theY direction, the electron beam 19 is scanned in a linear manner alongthe X direction. In such a case that a relatively small specified regionis inspected, a method for inspecting this small region by setting theformer stage to a stationary manner may be effectively employed, whereasin the case that a relatively wide region is inspected, such a methodfor inspecting this wide region by continuously moving the stages at aconstant speed may be effectively employed. When the electron beam 19 isrequired to be blanked, the electron beam 19 is deflected by theblanking deflecting device 13, and the electron beam 19 does not passthrough the diaphragm 14, so that the electron beam 19 can be controlledin such a way that the substrate 9 to be inspected is not irradiated bythe electron beam 19.

In this embodiment, as the position monitor length measuring device 34,such a length measuring device operated by way of laser interference hasbeen employed. As a result, both a position of the X stage 31 and aposition of the Y stage 32 can be monitored in real time, and thepositional information is supplied to the correction control circuit 43.Also, data as to rotation numbers of the respective motors for the Xstage 31, the Y stage 32, and the rotary stage 33 are similarly suppliedfrom the respective drivers to the correction control circuit 43. Thecorrection control circuit 43 can grasp a region and a position, onwhich the electron beam 19 is irradiated, based upon the above-describeddata. Also, a positional shift (positional deviation) of an irradiatingposition of the electron beam 19 is corrected in real time by thecorrection control circuit 43, if required. Also, such a region wherethe electron beam 19 has been irradiated may be stored every thesubstrate 9 to be inspected.

The measuring device 35 for measuring the height of the substrate to beinspected is arranged as follows: That is, while an optical typemeasuring device corresponding to a measuring system other than anelectron beam is employed, for instance, while either a laserinterference measuring device or a reflection light type measuringdevice for measuring a change at a position of reflection light isemployed, a change in heights of the substrate 9 to be inspected whichis mounted on the X stage 31 and the Y state 32 can be measured in realtime. In this embodiment, such a measuring system has been employed. Inthis measuring system, narrow white light which has passed through aslit is irradiated through a transparent window onto the substrate 9 tobe inspected, a position of reflection light is detected by a positiondetecting monitor, and thus, a change amount of heights is calculatedfrom a variation of the positions.

The focal distance of the objective lens 16 used to focus the electronbeam 19 in the narrow beam manner is dynamically corrected based uponthe measurement data of this inspecting-substrate-height measuringdevice 35, so that such an electron beam 19 which has been alwaysfocused onto an inspection region can be irradiated. Alternatively,while a camber and a height distortion of the substrate 9 to beinspected may be previously measured before an electron beam isirradiated thereonto, a correction condition of the objective lens 16every inspective region may be set based upon this measured data.

Next, a description is made of an arrangement of the image operationunit 5. An image signal of an inspection region of the substrate 9 to beinspected, which is detected by the secondary electron detector 20, isamplified by the preamplifier 21. After the amplified image signal isdigitized by the A/D converter 23, this digital image data is convertedinto an optical image signal by the optical converting means 23, andthen, this optical image signal is transferred by the opticaltransferring means 24 such as an optical fiber cable. The transferredimage signal is again converted into an electric image signal by theelectric converting means 25, and thereafter, this electric image signalis supplied to the control computer 6. Then, this electric image signalis stored into either the first image storage unit 51 or the secondimage storage unit 52 of the image operation unit 5 from the entirecontrol unit 65 of the control computer 6.

The comparing/calculating unit 53 of the image operation unit 5compares/calculates this stored image signal with another image signalstored in another image storage unit. The defect judging unit 54compares an absolute value of a difference image signal with apredetermined threshold value. This difference image signal correspondsto a result made by the comparing/calculating operation of thecomparing/calculating unit 53. In such a case that the signal level ofthe difference image is larger than the predetermined threshold value,the defect judging unit 54 judges this pixel as a defect candidate, anddisplays this judged pixel on the image display portion 56. Thisposition is displayed on the map display portion 55, and in the casethat a plurality of defects are extracted, a total number thereof, orthe like are displayed on this map display portion 55.

Next, a condition when an inspecting operation is carried out, namely,setting of a recipe during an inspecting operation will now beexplained. FIG. 2 is a screen diagram for indicating a display exampleof the image operation unit 5, namely represents an example in aninitial stage of an inspecting operation. The map display portion 55,the image display portion 56, and buttons for various sorts ofinstructions are displayed on the screen 50. The map display portion 55displays thereon a present position of a stage. The image displayportion 56 displays thereon an optical microscopic image which isacquired by the optical microscope unit 5 shown in FIG. 1, and an SEMimage which is acquired by the secondary electron detector 20. In theinitial stage of the inspecting operation within the example of FIG. 2,the optical microscopic image is displayed on the image display portion56. The mode switching portion 6 is located below the screen 50, and aplurality of buttons are being displayed on this mode switching portion6. For example, since a mouse pointer, or the like is fitted to aninspection button and this inspection button is clicked, the circuitpattern inspection apparatus 1 is set to an automatic inspectionexecuting mode. When a recipe is formed, since a button for forming arecipe is clicked, the present mode screen is changed into a recipeforming screen (will be explained later). In the screen region whereboth the map display portion 55 and the image display portion 56 arebeing displayed, contents to be displayed are changed by switching themodes.

Operation buttons which are commonly used on a plurality of screens aredisplayed on the right side of the image display portion 56, forinstance, “inspect”; “start”; “end”; “screen”; “print”; “confirmdefect”; “execute”; “unload”; “image store”, and the like are displayed.For example, when an image store button 66 is clicked, such a screen isdisplayed which designates a name used to store an image which ispresently displayed as an image file.

As to various sorts of parameters which are required so as to execute aninspecting operation, there are parameters specific to substrates to beinspected, and other parameters for determining operation conditions ofthe inspection apparatus 1.

The parameters specific to the substrate to be checked are mainlysubdivided into two sorts of parameters. One of these specificparameters is referred to as a “product sort parameter”, and thisproduct sort parameter corresponds to such a parameter having norelationship with a layer which is formed in a half way of amanufacturing process. This product sort parameter corresponds to, forexample, a wafer size; either an orientation flat or a shape of a notch;an exposing shot size of a semiconductor product; a chip (or die) size;a memory cell region; a size of a repetition unit of a memory cell; aninspection region, and the like. These items have been formed as a tableof “product sort file”, and have been stored in a memory, or the like.

Another parameter of the specific parameters is such a parameter calledas a “step file.” This “step file” parameter corresponds to such aparameter which is required to be adjusted, since materials of surfacesand states of shapes are different due to layers in a half way of amanufacturing process. For example, this “step file” parametercorresponds to an irradiation condition of an electron beam; varioussorts of gains for a detection system; a condition of image processoperation used to detect a defect. These parameters have been registeredas “step file.”

When an inspecting operation is carried out, since either a name or anumber is designated to which both this “product sort file” and the“step file” have been registered, such an inspection condition can becalled which corresponds to a specific semiconductor product and aspecific manufacturing step. In this embodiment, both “product sortfile” and “step file” are grouped to be referred to as a “recipe.” Also,a series of operations for inputting these various sorts of parametersand/or for registering these various sorts of parameters will bereferred to as “recipe forming.”

FIG. 3 is a flow chart for indicating sequential process operations of arecipe forming mode. Also, FIG. 4 is a screen diagram for indicating adisplay example when a recipe is formed. A recipe forming button of themode switching operation 60 located below the screen 50 is displayed ina different color from colors of other buttons, which indicates that therecipe forming mode is presently set. When a start button 67 located ata right portion of the screen 50 is pushed (step 301), for example, “setrecipe forming condition” is displayed on a guidance display portion 71located above the recipe forming mode screen 50 (step 302), and a shelfnumber is designated on a cassette shelf number display portion 72 whichis displayed in a left side of this screen 50. The designated shelfnumber is displayed in a color discriminatable manner. A pull-down menuof a product sort file setting portion 73 and a step file settingportion 74, which are displayed on the screen 50, are caused to berepresented so as to call a recipe file. Both a product sort filecondition and a step file condition are designated, or entered inresponse to a selecting operation, a newly setting operation, or achanging operation. Further, a lot ID of the relevant wafer and a waferID thereof are entered by using a lot ID setting portion 75 and a waferID setting portion 76 (step 304).

In this example, a changing operation of a recipe file implies such anoperation that a recipe forming condition is changed irrespective ofsuch a fact that a wafer is loaded. However, under normal condition, arecipe file is changed while a wafer is loaded.

Also, in the case that another recipe of another apparatus (will beexplained later) is used, since this recipe cannot be directly enteredin this inspection apparatus 1, the below-mentioned work is carried out.That is, defect information file (content of this file has been openedto user) as to an inspection result is entered, this entered defectinformation file is converted so as to form a recipe usable in the owninspection apparatus, and then, this formed recipe is changed in thisstep in order to supplement this shortage data.

Next, a wafer load button 68 is clicked in order that a wafercorresponding to the substrate to be inspected is loaded from a wafercassette which has been installed on a loader of the inspectionapparatus 1 (step 305). The inspection apparatus 1 detects either anorientation flat or a notch of the wafer, and holds the wafer on asample holder of a sample exchanging chamber, and then, transports thesample holder so as to mount this transported sample holder on a stageof an inspection chamber.

Next, a beam calibration button 69 is clicked in order to instruct abeam calibration. The inspection apparatus 1 moves the wafer to a stagereference mark, and executes an absolute calibration of an electron beam(step 306). This absolute calibration corresponds to such a calibrationexecuted based upon the normal default recipe file condition (step 306).In this absolute calibration, the electron beam is irradiated; adeflection correction is executed; a reference coordinate correction isperformed; and a focal point parameter correction is carried out.

Next, a contrast tab 77 located above the screen 50 is clicked so as toreplace the screen display by a contrast menu (not shown), the electronbeam is irradiated onto a position which is designated on the wafer, andthe image of the wafer is displayed in order to confirm contrast of thisimage. Thereafter, a focal point and astigmatism are readjusted (step307). In this case, alignment chips are pointed, and an origin of afirst chip is set under the optical microscope by which the monitordisplays an image, then an alignment mark position of the first chip ismoved to a position under the optical microscope in a manual mode. Then,after the microscope image has been registered, an acquisition of an SEMimage is instructed; the alignment mark position of the first chip ismoved to a position under the SEM in a manual manner and in a very fineadjusting mode; the acquired SEM image is registered; and the alignmentcoordinate is registered.

Next, a chip matrix tab 78 is clicked so as to display this screen (notshown), and a chip which should be inspected is designated (step 308).In this step, both a size and an array of the chip are inputted, andeither an inspection subject region of a wafer peripheral portion or acondition as to whether or not the chip is present is designated. Eitherthe inspection subject chip or the respective subject chip, which hasbeen set in this step, is stored in the step file in the new name.

Subsequently, an alignment tab 79 is clicked so as to display analignment screen (not shown), so that both an alignment condition isinputted and the alignment is executed (step 309). In this step, analignment chip is designated by way of a plurality of points; and ismoved to an origin of a first alignment chip; the optical microscope isswitched to the used monitor; and the alignment chip is moved to analignment mark position of the first alignment chip in a manual mode.Then, after the microscopic image has been registered, an acquisition ofan SEM image is instructed; the alignment chip is moved to the alignmentmark position in a manual manner and in a very fine adjusting mode; theacquired SEM image is registered; and the alignment coordinate isregistered.

As items for executing the alignment, the below-mentioned items areoperated: That is, (1) moving operation of first point; (2) imageinputting/searching/matching operations; (3) moving operation of secondpoint; (4) image inputting/searching/matching operations; (5)moving/searching/matching to remaining points; and (6)inclination/position/chip interval correction are carried out.

Also, as items of offset setting operation of chip origin, thebelow-mentioned items are operated: That is, (1) moving operation tofinal point alignment; (2) designating operation of alignment mark point(SEM image); (3) moving operation to first chip origin; (4) designatingoperation of chip origin position (SEM image); and (5) offsetcalculating/registering operation of chip origin-to-alignment mark arecarried out. In this case, an offset value of a chip origin implies sucha distance between an alignment coordinate and an origin coordinate of achip where this mark is present.

As previously explained, an offset value between a designatedalignment-purpose pattern coordinate and a chip origin is inputted so asto be registered as an alignment parameter within the step file. While arecipe is formed, since there are many parameters which are used todesignate coordinates on a wafer where various sorts of processoperations are carried out, an alignment condition is firstly definedand registered, and is executed until an alignment.

Next, a cell information tab 80 is clicked so as to switch the alignmentscreen into a cell information screen (not shown), and then, a memorycell region within a chip is set (step 310). As items for setting thememory cell region, a cell region is inputted; a cell pitch is inputted;and both the cell region and the cell pitch are registered. The cellregion is inputted by employing both an optical microscope image and anSEM image.

Next, a chip region setting operation is carried out on the same cellinformation screen (step 311). As items of chip region settingoperations, a chip region is inputted; a chip non-inspection region isinputted; and both the chip region and the chip non-inspection regionare registered. The chip region is inputted by employing both an opticalmicroscope image and an SEM image.

Next, an inspection tap 81 is clicked so as to display an inspectionregion designating screen (not shown), and then, an inspection region isdesignated (step 312). When an inspection region is designated, twosorts of inspection regions can be designated, namely, an inspectionsubject chip and an inspection region within a chip can be designated.In the case that all of chips formed on a wafer need not be inspected,or in such a case that only a specific region within a chip is wanted tobe inspected, the region which is wanted to be inspected may bearbitrarily designated. Alternatively, an inspection sampling ratio maybe designated, namely, a ratio of the area which is wanted to beinspected to all of the chips may be designated. Since such a functionis provided, only the region which is wanted to be inspected can bechecked, so that inspection time can be shortened. Also, such adesignation may be carried out as to whether a wafer is moved along theX direction, or the Y direction. The data as to the chip region and theinspection region are stored as the parameters within the step file.

When the designating operation of the inspection region is accomplished,a calibration tab 82 is clicked so as to display a calibration screen(not shown), and then, a calibration setting operation is carried out bywhich a brightness during inspecting operation is adjusted (step 313). Acalibration operation implies such an operation that while an image isacquired, a gain control and a brightness correction of an apparatus arecarried out in response to a signal amount based upon a brightnessdistribution. In an actual calibration operation, this calibratingoperation is carried out by designating a chip where the calibratingoperation is performed, and by designating a coordinate value within thechip. The coordinate value for executing the calibration, the gain ofthe brightness, and the offset value are stored as the parameters withinthe step file.

Next, an image is actually acquired under the various sorts ofconditions which have been set in the previous steps, and then, an imageprocessing condition for detecting a defect is set. First, a trialinspection tab 83 is clicked so as to display a setting screen of animage processing condition by way of trial inspection (not shown). Whenan SEM image is firstly acquired, a sort of filters used to filter adetection signal is selected. Then, an image of a small region within 1chip is acquired under the same condition as that of the actualinspection. In this case, this small region implies, for instance, sucha region having a length for a single chip and having a width of 100 μmequal to an operation width of an electron beam. After the image hasbeen acquired, a threshold value for judging a defect is entered, andthen, in such a case that there is a place which is judged as thedefect, an image of this place is displayed (step 314). Since this trialinspection operation is repeatedly carried out, an optimum parameter isdetermined (step 315). The parameters such as the threshold value andthe file, which have been set in this step, are stored as parameterswithin the step file.

With execution of the above-explained process operations, various sortsof parameters required in an inspection operation are set. However, withrespect to actual semiconductor wafers, manufactured qualities as to allof semiconductor chips are not made uniform due to process fluctuationswithin wafer planes and among manufacturing lots. Thus, there are manypossibilities that the image processing condition set only by the trialinspection as to the small region cannot establish a satisfactory imageprocessing condition, so that a threshold value used to judge a defectmust be determined by considering the process fluctuations.

As a consequence, in order that a final trial inspecting operation for asingle sheet of wafer is carried out based upon the formed recipe file,a final trail inspection tab 84 is clicked to display an image (notshown) of the final trial inspecting operation (step 316). In the finaltrial inspecting operation, while the stage is continuously moved in aconstant speed, an image acquiring operation is executed. While both aposition and a height where an electron beam is being irradiated aremonitored at the same time, a scanning operation of the electron beam iscorrected in real time. Then, secondary electrons are detected, adetected signal is processed by performing the A/D converting operation,the image based on the detected signal is stored into the image memory,and the image processing operation, the image comparing operation, andthe defect judging operation are executed. Also, a shift between thecontinuous move direction of the wafer and the deflection width of theelectron beam is corrected. As to defect extracted results obtained inthe final trial inspecting operation, positions of defects are displayedand a total number of these defects are displayed on the map displayportion 55 shown in FIG. 2. Both a defect detecting level and an errordetecting level are confirmed, and if the used recipe corresponds to afinally proper recipe, then both the inspection results and the varioussorts of parameters which have been so far entered are registered inboth the product sort file and the step file (step 317). Finally, an endbutton 70 is clicked, so that an unloading operation of this inspectedwafer is carried out (step 318). Thus, the recipe forming step isaccomplished (step 319).

FIG. 5 is a plan view for showing an array of chips on a substrate to beinspected. In an inspection apparatus of a circuit pattern using anelectron beam, in such a case that an image is acquired by irradiatingthe electron beam one time, the following problems may occur due to aproperty of a substrate to be inspected. That is, contrast of theacquired image is fluctuated, and also, sufficiently higher contrast asto a subject portion cannot be obtained, since the electron beam isirradiated one time. To solve the above-explained problems, one solvingmethod is performed in such a manner that since the same region of theimage is irradiated by the electron beams plural times, an irradiationenergy amount of the electron beams is increased. In this case, it is soassumed that a single transport of a substrate to be inspected which istransported along one direction while being scanned by an electron beamis referred to as a “line.” Thus, in the case of a single irradiatingoperation, after a scanning operation of 1 line is accomplished, thesubstrate to be inspected is transported by 1 line along a directionperpendicular to the line, and then, an adjoining line is irradiated byan electron beam, whereas in the case of a plural irradiating operation,1 line is irradiated plural times without transporting the substrate tobe inspected along the perpendicular direction.

However, if the irradiation energy amount is increased in such a method,then there is such a risk. That is, a potential is locally andtemporarily changed, so that a semiconductor wafer corresponding to thesubstrate to be inspected is destroyed. Also, since the same line isirradiated plural times, inspection time is delayed.

In this embodiment, as represented in FIG. 5, in such a case that aninspection subject chip indicated in a gray color among a plurality ofchips 85 is scanned by an electron beam, a transport direction of thesubstrate to be inspected during the electron beam scanning operation isperformed as illustrated by a transport direction 86 of a pre-scanningoperation.

In other words, a pre-irradiating operation is carried out one time asto all of inspection subject chips among chips arrayed in a firstcolumn. In this pre-irradiating operation, while the electron beam isscanned, the substrate to be inspected is transported over a length of 1line along the transport direction 86 of the pre-scanning operation, andsubsequently, is transported only over a distance equal to the width of1 line along the perpendicular direction. This process operation isrepeatedly carried out. Next, as to all of the inspection subject chipsamong the chips arrayed in the first column, an electron beam isirradiated so as to acquire an inspection image one time in a similarmanner to that of the pre-scanning operation, while the substrate to beinspected is transported along a direction indicated by a transportdirection 87 of an inspection scanning operation. Subsequently, as toall of the inspection subject chips among the chips arrayed in the firstcolumn, a post-irradiating operation is carried out one time in asimilar manner to that of the pre-scanning operation, while thesubstrate to be inspected is transported along a direction indicated bya transport direction 88 of a post-scanning operation. While a series ofthe above-described scanning operations is considered as one set, whenone set scanning operation is accomplished, the electron beam is blankedas represented in an electron move direction 89 in order not to beirradiated onto the substrate to be inspected. Then, the position of theelectron is moved to a starting point 90 of a pre-scanning operation fora pair of the next chip column. Then, a scanning operation of anelectron beam is repeatedly carried out in a similar manner with respectto each of pairs every chip column.

As previously explained, while the same line is not irradiated pluraltimes, either one chip or chips of one column are previously irradiatedby the electron beam plural times. Then, since images which have beenacquired when the chips for 1 column are irradiated are employed as theinspection images, temporal delays required for improving the chargingcondition may be produced, as compared with such a case that regions of1 line are irradiated plural times, so that local increases of thepotential can be prevented.

Also, when the irradiating operation for the chips of 1 column isrepeatedly carried out, since such electronic optical conditions as anacceleration voltage and an irradiation current amount are varied, thecharging conditions of the substrate to be inspected can be changed, andthus, more flexible inspecting operations can be realized. When thecharging conditions of the substrate to be inspected can be varied,contrast of such an image that defects thereof are emphasized can beobtained, so that an efficiency of the inspecting operations can beimproved.

Furthermore, when the irradiating operation for the chips of 1 column isrepeatedly carried out, a charging condition can be set to a desirablecharging condition by employing such a method. That is, a width of 1line is changed, widths of the respective lines are overlapped with eachother, and a width which is not scanned is provided between therespective lines. Also, as to 1 line, a transport direction during apre-irradiating operation is made coincident with a transport directionwhen an irradiating operation for acquiring an inspection image iscarried out, so that temporally uniform charges may be applied.

It should be understood that a post-irradiating operation may bealternatively omitted within 1 set. In this alternative case, such aphenomenon occurs. That is, electric charges are accumulated by theelectric charges produced in 1 set and irradiating operation for thenext set. When the electric charging effects are progressed, theelectron beam is deflected by an electric field, and contrast ofacquired images is changed every time a total number of irradiatingoperations is incremented, so that these images having the changedcontrast may be detected as pseudo-defects.

As a consequence, since a post-irradiating operation is carried outafter an irradiating operation for acquiring an inspection image hasbeen carried out within 1 set, a charging condition are accelerated inan earlier stage so as to be brought into a saturated condition, or acharging condition is returned to an original condition, depending uponan irradiation subject, so that qualities of entire images of asubstrate to be inspected may be made uniform, and thus, pseudo-defectsare not extracted.

FIG. 6 is a screen diagram for setting a parameter when a recipe isformed, namely, corresponds to such an operation screen. That is, withrespect to a pre-irradiating operation and a post-irradiating operation,an electro-optical condition such as an acceleration voltage and acurrent value is set; a scanning direction (namely, transport directionof substrate to be inspected) is set; and a repetition time, a scanningwidth, a scanning line pitch, and the like are set. When asetting/instruction inputting portion 91 of a pre-scanning operationimplying a pre-irradiating operation is clicked so as to make a checkmark, or a setting/instruction inputting portion 92 of a post-scanningoperation implying a post-irradiating operation is clicked so as to makea check mark, such a value which has been previously set in either aparameter input portion 93 of the pre-scanning operation or a parameterinput portion 94 of the post-scanning operation is displayed, and thisdisplayed value can be changed. When the value is confirmed, since asetting button 95 is clicked, the relevant parameter is set.

As previously described, in accordance with this embodiment of thepresent invention, since the irradiating method of the electron beam ismodified, the charging conditions of the substrate to be inspected canbe arbitrarily controlled, and a total number of the above-describedpseudo-defects contained in the defects which have been extracted basedupon the acquired images can be reduced. Therefore, there is such aneffect that reliability can be increased.

Also, since the chip inspection, the wafer extracting inspection, andthe like can be quickly carried out while monitoring the screen, such adefects occurred in the entire product, or a defect occurred in aspecific region can be quickly sensed. Also, the variation in theprocess conditions can be firmly sensed, and this condition variation isfed back to the process. At the same time, the process for manufacturingsemiconductor device can be uniformized to reduce extra cost.

Furthermore, since the inspection apparatus according to the presentinvention is applied to a substrate product process, abnormal values ofa product apparatus and/or a condition can be discovered in an earlierstage and in high precision with reference to the screen of theinspection apparatus. As a result, the abnormal condition solvingtreatment can be quickly realized in the substrate manufacturingprocess. As a result, failure rates as to semiconductor devices andother substrates can be reduced, and the productivity can be increased.

In accordance with the present invention, such a circuit patterninspection apparatus capable of arbitrarily controlling the chargingconditions of the substrate to be inspected can be provided, whileemploying the electron beam having high reliability.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1-6. (canceled)
 7. A method for inspecting a sample using an imageobtained by detection of secondary electron or reflected electrongenerated by an irradiation of focused electron beam, wherein saidmethod includes steps of irradiating the sample in which a plurality ofchip including a circuit pattern is two dimensionally arrayed with thefocused electron beam while moving the sample continuously by stage, anddetecting secondary electron or reflected electron, comprising: carryingout a set of irradiation of said arrayed chip by a scanning line that isformed by scanning the focused electron beam to a direction crossing themoving direction of the stage; wherein the carrying out of said set ofirradiation of the focused electron beam further comprises steps of: a)pre-scanning of said the scanning line by which said image is notobtained; and b) inspection scanning of said scanning line that iscarried out after said pre-scanning, by which said image is obtained. 8.A method for inspecting a sample, according to claim 7, furthercomprising: moving an irradiating position of the focused electron beamto neighboring scanning line from present scanning line in a directioncrossing to said present scanning line.
 9. A method for inspecting asample, according to claim 7, wherein at least one of an accelerationvoltage and irradiation current amount of said electron beam is variedbetween said pre-scanning and said inspection scanning.
 10. A method forinspecting a sample, according to claim 7, wherein a width of saidscanning line is varied between said pre-scanning and said scanning foracquiring the image.
 11. A method for inspecting a sample, according toclaim 7, wherein said scanning line is overlapped with neighboringscanning line.
 12. An inspection apparatus for inspecting a plurality ofchip or circuit pattern included in a sample with using an imageobtained by detecting secondary electron or reflected electron that aregenerated by an irradiation of focused electron beam while moving thesample continuously in one direction, said plurality of chip is twodimensionally arrayed in said sample, comprising: a stage for moving thesample; an electron-optical system for carrying out said irradiation ofthe focused electron beam and detection of the secondary electron orreflected electron, and a controlling computer that controls saidelectron-optical system to carry out a set of irradiation of the focusedelectron beam to a column of said arrayed chip by a scanning line thatis formed by scanning the focused electron beam to a direction crossingthe moving direction of the stage, wherein said set of irradiation ofthe focused electron beam includes: a) pre-scanning of said the scanningline by which said image is not obtained; and b) inspection scanning ofsaid scanning line that is carried out after said pre-scanning, by whichsaid image is obtained.
 13. An inspection apparatus, according to claim12, further comprising: an image operating unit that determines a defectcandidate on said sample by the comparison of images.